The purpose of this proposal is to request funds for the purchase of a Phillips CM120 Biotwin transmission electron microscope (TEM) with cryo and digital imaging capabilities for a user group of twenty-seven investigators. Due to the current lack of an accessible research TEM on campus, applicant investigators either have had to locate potential collaborators elsewhere, or curtail thoughts of EM experiments altogether. The instrument we request will support users' urgent needs for ultrastructural analysis; immunogold localization-investigations; and high resolution cryo studies on virus particles, two dimensional protein crystals, and macromolecular assemblies. Additionally, the CM120 will serve as the centerpiece for a university EM core imaging facility, which will be equipped preparation and accessory instruments, and also will house the Pathology department's scanning EM and twenty-five hear old TEM that is dedicated to clinical screening of hospital specimens. The OHSU administration has committed funds to the renovation of a centrally located space for the EM core and contributes salary support funds for technical help. The support staff and a three member Usage Oversight Committed will be available to help, advice and collaborate with users. Additionally, an important component of our application is the development of training plan for users, so that interested investigators with diverse backgrounds can prepare specimens and operate the TEM themselves. The multi-user facility environment will be eased by the user-friendly nature of the Biotwin and the electronic image capture option. The long term maintenance of the TEM will be insured by service contract guarantees from OHSU's Vollum Institute and Department of Microbiology; and EM core operations will be guided by a seven member Core Advisory Committee. We believe the ability to purchase the CM120 Biotwin will have a much large positive impact on the OHSU community than simply the instrument itself.